This invention relates to an ultrasonic recanalization system for ablation of atherosclerotic stenosis and plaques in human or animal atherosclerotic arteries, to be used in human or animal percutaneous and transcutaneous recanalization (angioplasty).
Several angioplasty techniques are known in the prior art. The most advanced techniques to date are those using balloon catheters, or those using laser angioplasty with specific laser systems, and those using a high speed rotary cutting blade technique.
The most advanced technologies in this art are described in the following documents:
EP 268,068 filed on 23 October 1986 describes an angioplasty balloon catheter.
Edwards Lis Division of Baxter has a commercial balloon catheter marketed as Hydracross.RTM..
Trimedyne Inc. has a laser angioplasty product marketed as Laserprobe.RTM..
U.S. Pat. No. 4,819,634 describes the use of the rotary blade catheter technique for atherectomy.
Lately scientists decided to apply ultrasonic techniques to recanalization (angioplasty).
Ultrasonic technology has been used widely in dentistry and there are many sophisticated techniques for applying ultrasonic transducers to different probes having to penetrate tissues inbetween teeth or gums. The modern equipment is supplied with efficient cooling systems and controls for both temperature frequency and amplitude of the ultrasonic energy emitted at the probe tips.
In surgery, ultrasonic technology has been used for many years; equipment such as Storz ultrasonic nephroscopic sheath (produced by Storz Endoscopy-America Inc.) has been used for a long while in urology for percutaneous nephrolithotomy to disintegrate calcium blocks. Saline at 4.degree. C. is used for cooling the overheated probe.
The complete procedure is discussed in an article published by M. G. Eugaras et al. in "The Journal of Thoracic and Cardiovascular Surgery 1988" 95:1038-40 demonstrating the advantage of the ultrasonic system.
Using double or triple lumen catheters to enter arteries and perform recanalization procedures by either of the known arts (balloon or laser) or by rotational thrombectomy, using a high speed rotary cutting blade inserted through a catheter into the artery, the blade minces the stenosis obstruction and, consequently enlarges the artery lumen. At this point, the technique of using the balloon can be applied. It was therefore an obvious development in the art to try to apply the sophisticated ultrasonic technology, using a double or triple lumen catheter with the modified ultrasonic probes to perform recanalization in arteries
The use of an ultrasonic angioplasty system is described in detail by R. Seigal et al., who published a detailed report "Ultrasonic Plaque Ablation for Recanalization or Occluded Arteries." The report was published in "Circulation," p. 1443, in December 1988.
C. Dobrinski et al. published their work on "Ultrasonic Angioplasty" in the journal "Archive des Maladies du Coeur," 1989; 82;377-80.
EP 316,796 published 24 May 1989 describes an ultrasonic device having an ultrasonic generator connected to a probe extending from the end of a catheter. The bulbous tip of the probe is placed against the blockage. A radiographic contrast fluid can be introduced into the catheter to make the blood vessel clearly visible on an X-ray monitor.
U.S. Pat. No. 4,808,153 published 28 February 1989 describes a device for removing plaque from arteries. The vibrations are transferred through a hollow member of an inert rigid material such as titanium. Several vibrating members are disposed around the hollow member, all activated by the ultrasonic frequency. A flexible catheter is disposed on the hollowed member, having a forward end covering the hollow member ending and having a blunt disposition.
WO 8,906,515 published 27 July 1989 describes an ultrasonic angioplasty device that employs a frequency generator, a piezoelectric transducer, and a horn. An ultrasonic transmission member is used to introduce the device into the patient's circulatory system. The ultrasonic transmission member is formed as a wire of aluminum or similar alloy in an annealed state.
In all these prior art works, it was clearly demonstrated that the ultrasonic technique for angioplasty is viable if carried out carefully without risking any damage to the inner surface of the arteries during the application and specifically when approaching the stenosis blocked sites, and, if appropriate, cooling is provided.
It is therefore the purpose of this invention to provide an ultrasonic recanalization system having sufficient controls and specific applicators which will minimize the risk of damage to the arteries before, during and after the ultrasonic ablation of the atherosclerotic plaques, as well as to assure that the stenosis splinters released during the application will not block the ultrasonic hollowed tip. The ultrasonic tip has appropriate cooling means on the inner and outer lumen.
The ultrasonic recanalization technique provided will enable ablation of peripheral and coronary atherosclerotic arteries in humans and animals. It may also be used in urology service for percutaneous nephrolithomy decalcification, as well as decalcification of blockages in the pancreas, etc.